Centrifugal fan or blower



L. WEISS ET AL CENTRIFUGAL FAN OR BLOWER Filed Aug. 29. 1921 Patented Dec. 2, 19249 UNITED STAT LEO WEISS AND EUGEN MANDLER, F VIENNA, AUSTRIA.

OENTRIFUGAL FAN OR BLOWER.

Application filed August 29, 1921. Serial No. 496,226.

(GRANTED UNDER THE PROVISIONS OF TIE-IE ACT OF MARCH 3, 1921, 41 STAT. 15., 1313.)

To all whom it may concern:

Be it known that we, LEO WEISS, a subject of Austria, and Essen MANDLER,

residing at Vienna, Austria,

"a subject of Czechothe well-known fact that sure of a centrifugal fan form speed increases up when a portion of the air the delivery presrunning at a unito a certain point leaving the wheel is allowed to escape instead of the full quantity of ai being allowed to flow into the air channels.

The invention will now be more particularly explained withreference to the accompanying the blades of which are drawings illustrating a ventilator,

curved and tilted forward. It is known that with such centrifugal fans the amount of centrifugal power used to obtain pressure is comparatively small and that the pressure is obtained to a large extent from the velocity of the air or gas discharged by the wheel, which velocity increases with the amount of gas that asses through the wheel, as will be seen om the diagram illustrated in Figure 2 in connection with the outlet conditions. 111 the latter diagram, of is the circumferential speed, to the relative an d c the resultant velocity of discharge. If a portion of the air discharged by the wheel is allowed to escape then the amount of air passing through the fan will be greater than previously and 10 will become greater, thereby causing in its turn an increased velocity ofthe air it lea es he fan blades.

The present invention is based on the fact that the increase in pressure will be more,

the smaller the resistance which the escaping air has to overcome. In order correspondingly to reduce this resistance, according to the present invention, the air is discharged through a diffuser viz :througha channel of gradually increased section. Such a diffuser reduces the outlet resistance whereby the greater part of the velocity energy of the escaping air is recovered at the same time as pressure energy so that the total eiliciency of the ventilator is only slightly i111- paired, As is well known the velocity is greater and therefore the pressure lower at the narrow part of the diffuser than at, the enlarged outlet section thereof and consequently the ventilator has to work only against this lower pressure.

For the reduction of the outlet resistance it is further of advantage that the air should escape immediately it leaves the ventilator blades so that the total capacity of the ventilator need not be used to overcome both the frictional and pressure resistance of the ventilator casing.

According to the invention the air is allowed to escape by one or more annular orifices arranged concentrically with the shaft of the ventilator on the ventilator casing being opened, these orifices being opened and adjusted by means of a throttling arrangement.

By varying the quantity of escaping air the pressure of the fan is regulated without its speed being varied, such a regulation being much more economical than the usual one by which the whole quantity of discharged air is t'hrottled since in the latter system of regulation the ventilator has to revolve at a speed corresponding to the highest pressure so that the reduction of pressure energy- In contra-distinction hereto, in the present invention the ventilator can rotate at a Speed h ch g es just sufficient pressure fo the average continuous output-and can only be obtained by loss of the air which the escaping air partly converts its' the pressure can be increased gradually in the manner described. In order to render this clearer, we will give a particular example A cupola fan of usual construction running at a constant speed has to overcome under the average working conditions a pressure of 500 m/m W. Now in order to allow for any forced working such a fan must have a speed corresponding to a pressure of 600 m/m W. G. so that in order to obtain the required delivery head of 500 111/111 TV. G. for average working, the air channel has to be throttled by means of a damper. This constant throttling however, means a constant loss of energy. In contradistinction thereto according to this invention the fan will receive only a speed necessary for 500 m/m V. G. and the effect for temporarily obtaining a higher pressure of say 600 m/m W. G. is obtained in a very simple way viz :by allowing a portion of to escape in the manner above referred to.

' In the accompanying drawing Figure 1 is a vertical sectional view of an apparatus constructed in accordance with the invention.

Fig. 2 is a diagram illustrating a principle of the invention.

Figure 1 in the accompanying drawing illustrates this arrangement, by way of ex ample, as applied to a ventilator. For the escaping of the air an annular opening or gap .9 is provided on the driven side of the wheel a revolving in a spiral casing Z2 which opening is formed by a bearing shield 0 being fixed at a suitable distance from the wall of the casing d. If desired the amount of escaping air may be regulated, for instance, by means of a damper e which permits the annular opening referred to, to be more or less closed according to requirements by its axial displacement.

An annular opening .9 is also provided on the suction side of the fan between the wall of the casing g and the suction plate f. In spite of the vacuum existing in the interior of the fan wheel in this arrangement only a very small quantity of air will flow back thereto from the casing 6, since the air having once passed the blades, it rotates and in consequence of its centrifugal force it can be forced radially inwards only with difficulty. However communication between the suction and the outlet side can be completely shut off for instance, by suitably forming the suction plate as is indicated by the dotted line on the lower end of Figure 1. By sufficiently extending the suction plate f and the wall of the casing g radially, the space 8 between them is caused to act asan expanding diffuser in velocity into pressure, which means that as the fan wheel as already hereinbefore referred to has to deliver a smaller pressure, can do this by a correspondingly reduced amount of work in order to accelerate the flow of the escaping air.

It is to be understood that this kind of diffuser may be replaced by any other kind as for instance guide vanes, spiral casings etc.

On the suction side of the blower, the quantity of air escaping from the casing Z) may be regulated and consequently also the pressure produced by the blower, by adjusting the distance between the suction plate and the wall of the casing g. In order to facilitate accurate adjustment, the suction plate 7 is provided with four helical slits it engaging with studs z'secured to the casing.

By turning the suction plate by means of a handle is the plate is displaced in its axial direction and the greater the distance between the suction plate and the wall of the casing, the more air can escape and the higher will then be to a certain extent the pressure produced by the blower.

It is also to be pointed out that after the air has escaped through the diffuser s it can be conducted back to the suction side of the ventilator or be taken to a vacuum space. This however, does not form part of the present invention.

Vhat we claim is 1. The combination with a centrifugal fan having means for permitting the escape of a portion of the fluid discharged by the fan blades, and a diffuser through which,

said portion of air is allowed to escape.

2. A combination as claimed in claim 1 in which the diffuser includes expanding exhaust passages through which said portion of air is allowed to, escape.

3. A combination as claimed in claim 1 in which the diffuser includes an annular orifice arranged concentrically with the axis of the fan, and a valve mechanism for varying the area of said orifice.

4. A combination as claimed in claim 1 in which the diffuser is formed by one wall of the fan casing and by a suction plate arranged adjacent said wall, said plate being provided with'slanting slots, and fixed pins engaging said slots, plate will cause axial movement of the latter toward oraway from the fan.

5. In combination, a centrifugal fan including a casing, a bladed rotor arranged in said casing, to the interior of said rotor, and a diffuser through which a portion of the air forced by said rotor is adapted to escape after passing through the rotor, said'casing being provided with an ordinary outlet through which the major portion of the air driven by the rotor is' adapted to be discharged from said casing.

whereby rotation of said means for admitting air- 6. The combination with a centrifugal fan casing having a main air outlet and c2;- haust apertures, a plate fixed to one side of said casing and extending outwardly beyond one of said apertures, a valve ring for regulating the discharge of air passing between said plate and one side of the casing, a bladed rotorarranged in the casing, pins fixed to said casing, and a difluser plate adjustably connected to said pins and hav- 10 ing an outlet arranged Within said rotor.

In testimony whereof We have signed our names to this specification.

ING. LEO WEISS. ING. EUGEN MANDLER. WVitnesses J OSEF SC MIDT, Momrz SoHMoLKA. 

